After development of more than forty years, the current Internet based on Transmission Control Protocol/Internet Protocol (TCP/IP) (i.e. a network communication protocol) has achieved a great success, been closely related to people's life and become one of indispensable infrastructures in work, study and life of people. The TCP/IP-based Internet initially adopts a specialization and organization principle that “a network/network equipment performs simple processing and a host (host side) performs complex processing”, which causes formation of a current situation of a current Internet system structure: an application layer protocol on the host side may are conveniently and flexibly modified and deployed, so that the software in the application layer is developed rapidly, and functions of an application layer are greatly enriched; and a network layer forms sharp contrast with the application layer, and a network layer protocol is simple in design, poor in extensibility and difficult to modify. Thus, the following problems are caused:
on one hand, many fatal bugs of the network layer of the Internet are unlikely to be repaired and improved for a long time, for example: network management is difficult to deploy, network security problems become more and more serious, it is difficult to provide quality of service for a user by a best-effort forwarding strategy, and multicast is difficult to deploy and use; and
on the other hand, new protocols and new applications making revolution requirements on the network layer are difficult to implement, for example: it is relatively difficult to transit Internet Protocol version 4 (IPv4) to IPv6, access equipment increasingly challenges network reliability and differentiated service capability in terms of mobility and heterogeneity, routing is confronted with a problem about extensibility under a large-scale network condition, applications such as cloud computation and content delivery makes new requirements on network forwarding efficiency, and Vinton G Cerf, father of TCP/IP, also points out that the Internet should be better in terms of network security and network reliability (“security and reliability are the two most basic thresholds for advancing to the future Internet, otherwise the architecture may not survive”). Therefore, the Internet forms the situation that “the application network is flexible and variable, but the network layer stiff, difficult to change and full of bugs” at present. In order to solve the current problems and difficult situation of the Internet, deep discussion, researches and innovation from layers such as the network system structure and a control layer are required.
For how to solve the problems of challenges with which the current Internet is confronted, domestic and international research institutes make a lot of active exploration and researches from the Internet system structure layer. The Internet is developed mainly in two stages, and improvement in the Internet may be divided into two: evolution improvement and revolution improvement.
For many years, many problems about quality of serving guarantee, mobility support, high efficiency, reliability, security guarantee and the like of a conventional IP network are exposed, these problems are respectively solved by designing pertinent repair manners in the field of researches, and weaknesses or errors of a running network are immediately improved once being discovered, for example: a new protocol and functional component and the like are added in a conventional Internet system structure. Such a “repair->problem discovery->modification” improvement manner, the existing network is gradually evolved and developed on the basis of an existing TCP/IP system structure of the Internet, and new functions and characteristics are added to solve the current problems; and such a manner is an evolution improvement manner. Such an improvement manner has the advantages of easiness in deployment and implementation and favourability for protecting the existing input in the conventional Internet construction. However, the manner has main shortcomings as follows: 1) only local problems are solved within a small range by certain repair; 2) existing improvement may create benefits in a short period, but is destructive for a long time, for example: a Network Address Translation (NAT) technology is locally beneficial but integrally destructive; 3) certain repair may be unlikely to be “compatible” with continuous modification in the future; 4) after multiple repair, the Internet becomes “heavier and heavier” and more and more complex, flexibility is reduced, and bearing capacity of an originally-designed simple system structure of the Internet is exceeded; and 5) some inherent problems in the conventional Internet system structure are unlikely to be radically solved. At present, the Internet is gradually improved mainly in the “evolution” manner.
Since 2005, another point of view is gradually formed in the field of researches, the problems with which the IP network is confronted may be radically solved only by redesigning the network system structure, now is a good time for completely revolving the Internet system structure “Clean-Slate”, the existing Internet system structure is completely abandoned, and a new-generation Internet system structure integrating multiple design targets is designed. Such a solution aims to radically solve various problems of the existing Internet system structure, and is a revolution improvement solution. Such a solution has the advantages that: 1) leash of a TPC/IP system structure can be slipped, and constraints and framework of the system structure can be broken to solve left problems caused by the system structure of the Internet over many years; and 2) the Internet can be completely redesigned, many problems of the Internet can be overall solved, and many new requirements of the Internet can be overall met. However, the solution has the shortcomings that: 1) the completely new network may not be compatible with the existing Internet, and infrastructure of the existing Internet is required to be completely replaced, so that problems about network deployment and smooth transition exist; 2) there are great risks in how to establish a new system structure and whether problems with which the Internet is confronted at present and to be confronted in the future can be solved or not after the new system structure is established; and 3) it is necessary to reconstruct a test network suitable for the completely new system structure, so that evolution cost is higher.
In order to solve the problems of the current Internet and rapidly and flexibly deploy a new network protocol, an open programmable network is proposed, and the open programmable network refers to allowing a network researcher, besides an equipment manufacturer, to perform program on network equipment and manage a network system structure or network protocol. The open programmable network is one of representative achievements of the revolution improvement solution, and it may substantially be summarized as follows: an original integrated and complex Metropolitan Area Network (MAN) or Wide Area Network (WAN) or network equipment with multiple coexisting functional networks is functionally segmented, for example, into a data forwarding part and a logic control part, or a system core part and a user function part, and the like. An interface between each part is open and standard. On the basis of the open and standard interface, each part may be independently evolved and improved without notifying or influencing the other parts, so that the whole network or network equipment may be independently and smoothly evolved and improved. The open programmable network faces challenges as follows: 1) network layers are required to have certain reasonability, scientificity and extensibility; 2) scientific and extensible interlayer interfaces are defined; and 3) if a centralized control manner is adopted for the control layer, it is necessary to consider inter-area connection, extensibility (for example: global extension) and the like.
In terms of researches on an open programmable network, technologies such as a Software Defined Networking (SDN) technology proposed by Scott Shenker and the like in Berkeley University and OpenFlow (OpenFlow is a novel network switching model proposed by the revolution group) of Stanford University are representative achievements of open network researches. FIG. 1 is a topology diagram of an SDN/OpenFlow network, wherein the SDN/OpenFlow network includes three layers: an infrastructure layer, a network control layer and an application layer. The infrastructure layer of the SDN/OpenFlow network consists of each piece of forwarding equipment, and the forwarding equipment is simpler and free of a complex control plane compared with a router, switch and each gateway in a current network, and mainly works to forward a data stream. Main equipment of the network control layer is a network operating system (or called an SDN/OpenFlow controller), the network operating system simultaneously controls multiple pieces of forwarding equipment instead of an original independent control plane in each piece of equipment and even a current network management system through standard interfaces, and may implement network management and end-to-end data stream rule transmission (that is, a stream rule is transmitted to multiple pieces of forwarding equipment on a forwarding path), and in addition, the network operating system interacts with the application layer through an Application Programming Interface (API). The application layer consists of different applications, and the applications may directly call a network management and control function of the control layer through the API.
Like a deployment of another revolution improvement technology, an operator network inevitably encounters many problems in a process of evolution to an SDN/OpenFlow architecture, extensibility mentioned above is one of the most important problems, but network deployment flexibility is an important index for balancing the extensibility of the network. In a current SDN/OpenFlow network, network control layer equipment (for example: a controller) and infrastructure layer equipment (i.e. forwarding equipment) interact with each other through an IP-address-based communication protocol message (for example: OpenFlow protocol), and IP addresses of the controller and the forwarding equipment are both preconfigured, which are unfavourable for large-scale rapid deployment of the forwarding equipment and subsequent flexible addition and reduction of the forwarding equipment. For the problems, there is yet no effective solution.